N=int(input())


x=N
import math 
L=math.floor(math.sqrt(x)) # 平方根を求める

Primelist=[i for i in range(x+1)]
Primelist[1]=0 # 1は素数でないので0にする.
 
for i in Primelist:
    if i>L:
        break
    if i==0:
        continue
    for j in range(2*i,x+1,i):
        Primelist[j]=0

Primes=[Primelist[j] for j in range(x+1) if Primelist[j]!=0]
Primes.reverse()

from functools import lru_cache
@lru_cache(maxsize=None)
def calc(N,i):
    #print(N,i)
    if N==0:
        return 0
    if i>=len(Primes) or Primes[i]>N:
        return -1<<60
    
    ANS=0
    for j in range(i,len(Primes)):
        if N-Primes[j]>=0:
            ANS=max(ANS,calc(N-Primes[j],j+1)+1)

    return ANS

print(calc(N,0))